阅读说明：本技术 实现谐波抑制的变频电路、变频器、压缩机及空调设备 (Frequency conversion circuit, frequency converter, compressor and air conditioning equipment for realizing harmonic suppression ) 是由 刘华 黄伟 宋政璋 于 2021-08-25 设计创作，主要内容包括：本发明公开实现谐波抑制的变频电路、变频器、压缩机及空调设备。其中,该实现谐波抑制的变频电路包括依次设置在交流电源和负载之间的整流模块、母线电容和逆变模块,整流模块通过其内部的整流元件导通或截止,进而控制所述交流电源的各相之间的导通状态；该变频电路还包括：谐振模块,输入端连接所述交流电源,输出端连接所述整流模块；用于根据所述交流电源的各相之间的导通状态改变自身的充放电状态,进而触发所述整流模块内部的整流元件导通或截止。通过本发明,能够实现减小整流元件的截止角,从而减小电流畸变,使变频电路的输入电流更加接近正弦波,可以最大程度地抑制输入电流的谐波含量,实现功率因数校正作用。(The invention discloses a frequency conversion circuit, a frequency converter, a compressor and air conditioning equipment for realizing harmonic suppression. The frequency conversion circuit for realizing harmonic suppression comprises a rectification module, a bus capacitor and an inversion module which are sequentially arranged between an alternating current power supply and a load, wherein the rectification module is conducted or cut off through a rectification element in the rectification module so as to control the conduction state between each phase of the alternating current power supply; the frequency conversion circuit further includes: the input end of the resonance module is connected with the alternating current power supply, and the output end of the resonance module is connected with the rectification module; and the rectifier module is used for changing the self charge-discharge state according to the conduction state between the phases of the alternating current power supply so as to trigger the conduction or the cut-off of the rectifier element in the rectifier module. The invention can reduce the cut-off angle of the rectifier element, thereby reducing the current distortion, leading the input current of the frequency conversion circuit to be closer to a sine wave, being capable of restraining the harmonic content of the input current to the maximum extent and realizing the power factor correction function.)

1. The frequency conversion circuit for realizing harmonic suppression comprises a rectification module, a bus capacitor and an inversion module which are sequentially arranged between an alternating current power supply and a load, and is characterized in that the rectification module is conducted or cut off through a rectification element in the rectification module so as to control the conduction state between phases of the alternating current power supply;

the frequency conversion circuit for realizing harmonic suppression further comprises: the input end of the resonance module is connected with the alternating current power supply, and the output end of the resonance module is connected with the rectification module; the resonance module is used for changing the charging and discharging state of the resonance module according to the conducting state between the phases of the alternating current power supply, and further triggering the rectifier element in the rectifier module to be conducted or cut off.

2. The frequency conversion circuit for realizing harmonic suppression according to claim 1, wherein the ac power supply is a three-phase ac power supply;

the rectification module is specifically configured to: when the value of the direct current bus current is smaller than or equal to a preset threshold value, triggering a rectifier element inside the resonance module to be switched on or switched off according to the value of the direct current bus current and the charging and discharging state of the resonance module so as to realize that any two phases in the alternating current power supply are switched on at intervals of preset time and are switched off after the preset time lasts; and is also used for: when the value of the direct current bus current is larger than a preset threshold value, a rectifier element inside the resonance module is triggered to be switched on or switched off according to the charging and discharging states of the resonance module, so that each phase of the alternating current power supply is alternatively switched on independently with any one of the other two phases or is switched on simultaneously with the other two phases.

3. The frequency conversion circuit for achieving harmonic suppression according to claim 2, wherein the resonance module comprises:

the first inductor is connected in series with a first phase of the alternating current power supply, the second inductor is connected in series with a second phase of the alternating current power supply, and the third inductor is connected in series with a third phase of the alternating current power supply;

the first capacitor is connected between a first phase of the alternating current power supply and a second phase of the alternating current power supply, the second capacitor is connected between the second phase of the alternating current power supply and a third phase of the alternating current power supply, and the third capacitor is connected between the first phase of the alternating current power supply and the third phase of the alternating current power supply.

4. The frequency conversion circuit for realizing harmonic suppression according to claim 3,

the first inductor, the second inductor and the first capacitor form a charge-discharge loop for charging and discharging the first capacitor;

the second inductor, the third inductor and the second capacitor form a charge-discharge loop for charging and discharging the second capacitor;

the first inductor, the third inductor and the third capacitor form a charge-discharge loop for charging and discharging the third capacitor.

5. The frequency conversion circuit for realizing harmonic suppression according to claim 3, wherein the rectifier module comprises three rectifier bridges arranged in parallel, namely a first rectifier bridge, a second rectifier bridge and a third rectifier bridge;

the upper bridge arm of each rectifier bridge and the lower bridge arms of the other two rectifier bridges form different conduction loops respectively, and the conduction loops are used for controlling conduction between any two phases of the alternating current power supply.

6. The frequency conversion circuit for realizing harmonic suppression according to claim 5,

the upper bridge arm of the first rectifier bridge is composed of a first rectifier element, the lower bridge arm of the first rectifier bridge is composed of a fourth rectifier element, and the first phase of the alternating current power supply is connected between the upper bridge arm and the lower bridge arm of the first rectifier bridge;

an upper bridge arm of the second rectifier bridge is composed of a third rectifier element, a lower bridge arm of the second rectifier bridge is composed of a sixth rectifier element, and a second phase of the alternating current power supply is connected between the upper bridge arm and the lower bridge arm of the second rectifier bridge;

and the upper bridge arm of the third rectifier bridge is composed of a fifth rectifier element, the lower bridge arm of the third rectifier bridge is composed of a second rectifier element, and the third phase of the alternating current power supply is connected between the upper bridge arm and the lower bridge arm of the third rectifier bridge.

7. The frequency conversion circuit for achieving harmonic suppression according to claim 6, wherein the rectification module is an uncontrolled rectification module.

8. The frequency conversion circuit for realizing harmonic suppression according to claim 3, wherein the first capacitor, the second capacitor and the third capacitor are AC thin film capacitors.

9. A frequency converter comprising the frequency conversion circuit for realizing harmonic suppression according to any one of claims 1 to 8.

10. A compressor comprising a load which is an electric motor, characterized by further comprising the inverter of claim 9.

11. An air conditioning apparatus, characterized by comprising the compressor of claim 10.

Technical Field

The invention relates to the technical field of electronic power, in particular to a frequency conversion circuit, a frequency converter, a compressor and air conditioning equipment for realizing harmonic suppression.

Background

At present, high-power air conditioning equipment adopts three-phase alternating current for power supply. The traditional ac-dc-ac frequency conversion circuit generally adopts a three-phase uncontrolled rectifier circuit, fig. 1 is a waveform diagram of an output current of the existing frequency conversion circuit adopting the uncontrolled rectifier circuit, as shown in fig. 1, a cut-off angle exists in a rectifier element in the uncontrolled rectifier circuit, so that the distortion of an input current is serious, a large amount of harmonic waves are generated, and an input power factor is reduced. These nonlinear harmonic sources cause serious pollution to the power system and are also important factors that jeopardize the safe operation of the power grid. The harmonic processing method adopted at present is a high-frequency PWM (Pulse Width Modulation) rectification technology, and compared with a three-phase rectification element rectification circuit, an IPM (intelligent power module) is added in the high-frequency PWM rectification, so that the cost is higher, the control difficulty is increased, and the competitiveness is lacked in the frequency conversion air conditioner market.

Aiming at the problem that the input current of a frequency conversion circuit adopting an uncontrolled rectifying circuit in the prior art is seriously distorted and can generate a large amount of harmonic waves, an effective solution is not provided at present.

Disclosure of Invention

The embodiment of the invention provides a frequency conversion circuit, a frequency converter, a compressor and air conditioning equipment for realizing harmonic suppression, and aims to solve the problem that a large amount of harmonic waves are generated due to serious input current distortion of the frequency conversion circuit adopting an uncontrolled rectifying circuit in the prior art.

In order to solve the above technical problem, the present invention provides a frequency conversion circuit for realizing harmonic suppression, including a rectification module, a bus capacitor and an inversion module sequentially arranged between an ac power supply and a load, where the rectification module is turned on or off by a rectification element inside the rectification module to further control the on-state between phases of the ac power supply, and the frequency conversion circuit for realizing harmonic suppression further includes:

the input end of the resonance module is connected with the alternating current power supply, and the output end of the resonance module is connected with the rectification module; the resonance module is used for changing the charging and discharging state of the resonance module according to the conducting state between the phases of the alternating current power supply, and further triggering the rectifier element in the rectifier module to be conducted or cut off.

Further, the alternating current power supply is a three-phase alternating current power supply; the rectification module is specifically configured to: when the value of the direct current bus current is smaller than or equal to a preset threshold value, triggering a rectifier element inside the resonance module to be switched on or switched off according to the value of the direct current bus current and the charging and discharging state of the resonance module so as to realize that any two phases in the alternating current power supply are switched on at intervals of preset time and are switched off after the preset time lasts; and is also used for: when the value of the direct current bus current is larger than a preset threshold value, a rectifier element inside the resonance module is triggered to be switched on or switched off according to the charging and discharging states of the resonance module, so that each phase of the alternating current power supply is alternatively switched on independently with any one of the other two phases or is switched on simultaneously with the other two phases.

Further, the resonance module includes:

the first inductor is connected in series with a first phase of the alternating current power supply, the second inductor is connected in series with a second phase of the alternating current power supply, and the third inductor is connected in series with a third phase of the alternating current power supply;

the first capacitor is connected between a first phase of the alternating current power supply and a second phase of the alternating current power supply, the second capacitor is connected between the second phase of the alternating current power supply and a third phase of the alternating current power supply, and the third capacitor is connected between the first phase of the alternating current power supply and the third phase of the alternating current power supply.

Further, the first inductor, the second inductor and the first capacitor form a charge-discharge loop for charging and discharging the first capacitor;

the second inductor, the third inductor and the second capacitor form a charge-discharge loop for charging and discharging the second capacitor;

the first inductor, the third inductor and the third capacitor form a charge-discharge loop for charging and discharging the third capacitor.

Furthermore, the rectifier module is an uncontrolled rectifier module and comprises a first rectifier bridge, a second rectifier bridge and a third rectifier bridge which are arranged in parallel;

the upper bridge arm of each rectifier bridge and the lower bridge arms of the other two rectifier bridges form different conduction loops respectively, and the conduction loops are used for controlling conduction between any two phases of the alternating current power supply.

Furthermore, an upper bridge arm of the first rectifier bridge is composed of a first rectifier element, a lower bridge arm of the first rectifier bridge is composed of a fourth rectifier element, and a first phase of the alternating current power supply is connected between the upper bridge arm and the lower bridge arm of the first rectifier bridge;

an upper bridge arm of the second rectifier bridge is composed of a third rectifier element, a lower bridge arm of the second rectifier bridge is composed of a sixth rectifier element, and a second phase of the alternating current power supply is connected between the upper bridge arm and the lower bridge arm of the second rectifier bridge;

and the upper bridge arm of the third rectifier bridge is composed of a fifth rectifier element, the lower bridge arm of the third rectifier bridge is composed of a second rectifier element, and the third phase of the alternating current power supply is connected between the upper bridge arm and the lower bridge arm of the third rectifier bridge.

Further, the rectification module is an uncontrolled rectification module.

Further, the first capacitor, the second capacitor and the third capacitor are alternating current thin film capacitors.

The invention also provides a frequency converter which comprises the frequency conversion circuit for realizing harmonic suppression.

The invention also provides a compressor, which comprises a load, wherein the load is a motor, and the compressor also comprises the frequency converter.

The invention also provides air conditioning equipment comprising the compressor.

By applying the technical scheme of the invention, the self charge-discharge state of the resonance module is changed according to the conduction state between the phases of the alternating current power supply, and then the rectification element in the rectification module is triggered to be switched on or switched off, so that the cut-off angle of the rectification element can be reduced, the current distortion is reduced, the input current of the frequency conversion circuit is closer to a sine wave, the harmonic content of the input current can be inhibited to the greatest extent, and the power factor correction effect is realized.

Drawings

FIG. 1 is a waveform diagram of an output current of a conventional inverter circuit using an uncontrolled rectifier circuit;

FIG. 2 is a circuit topology diagram of a conventional AC-DC-AC frequency conversion circuit;

FIG. 3 is a block diagram of a frequency conversion circuit implementing harmonic suppression in accordance with an embodiment of the present invention;

FIG. 4 is a block diagram of a frequency conversion circuit implementing harmonic suppression in accordance with another embodiment of the present invention;

FIG. 5 is a waveform diagram of an input current of an AC power source according to an embodiment of the present invention;

fig. 6 is a graph comparing an actual waveform of an input of a frequency conversion circuit for achieving harmonic suppression with a sine wave according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be understood that although the terms first, second, third, etc. may be used to describe … … in embodiments of the present invention, these … … should not be limited to these terms. These terms are used only to distinguish … …. For example, the first … … can also be referred to as the second … … and similarly the second … … can also be referred to as the first … … without departing from the scope of embodiments of the present invention.

The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.

Alternative embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Example 1

As shown in fig. 1 mentioned above, in the inverter circuit using the uncontrolled rectifying circuit, there is a cut-off angle in the rectifying element in the uncontrolled rectifying circuit, which causes a serious distortion of the input current, and a large amount of harmonics are generated, resulting in a reduction in the input power factor. These nonlinear harmonic sources cause serious pollution to the power system and are also important factors that endanger the safe operation of the power grid, fig. 2 is a circuit topology diagram of a traditional ac-dc-ac frequency conversion circuit, wherein U, V, W is a three-phase ac input, and the circuit topology diagram further comprises a high-frequency PWM rectification module and an inverter module, a bus capacitor C and a load externally connected with a compressor. Compared with the traditional rectifying and inverting topological structure, the high-frequency PWM rectifying module is added, and a peripheral circuit is needed to control the on and off of the IGBT. The added circuit and module not only increase the cost of the controller and improve the software control difficulty, but also influence the reliability of the controller. Therefore, it is obvious that there are many disadvantages in the method of eliminating the harmonic wave by providing the high frequency PWM rectification module.

The present embodiment provides a frequency conversion circuit for realizing harmonic suppression, and fig. 3 is a structural diagram of a frequency conversion circuit for realizing harmonic suppression according to an embodiment of the present invention, and as shown in fig. 3, the frequency conversion circuit for realizing harmonic suppression includes a rectification module 2, a bus capacitor C, and an inverter module 3, which are sequentially disposed between an ac power supply and a load, the rectification module 2 is turned on or off by a rectification element inside the rectification module, so as to control a conduction state between phases of the ac power supply, and the frequency conversion circuit for realizing harmonic suppression further includes:

the input end of the resonance module 1 is connected with an alternating current power supply, and the output end of the resonance module is connected with the rectification module 2; the resonance module 1 is used for changing the charging and discharging state of the resonance module according to the conducting state between the phases of the alternating current power supply, and further triggering the rectifier element inside the rectifier module 2 to be conducted or cut off.

The frequency conversion circuit for realizing harmonic suppression of the embodiment changes the charging and discharging states of the resonance module 1 according to the conduction state between the phases of the alternating current power supply, and then triggers the conduction or the cut-off of the rectifier element in the rectifier module 2, so that the cut-off angle of the rectifier element can be reduced, the current distortion is reduced, the input current of the frequency conversion circuit is closer to a sine wave, the harmonic content of the input current can be suppressed to the maximum extent, and the power factor correction effect is realized.

Example 2

In this embodiment, the ac power supply is a three-phase ac power supply, and the rectifier module 2 is specifically configured to: when the value of the direct current bus current is smaller than or equal to a preset threshold value, triggering a rectifier element inside the resonance module 1 to be switched on or switched off according to the value of the direct current bus current and the charging and discharging state of the resonance module, so that any two phases in the alternating current power supply are triggered to be switched on at intervals of preset time and switched off after the preset time is continued; when the value of the direct current bus current is larger than the preset threshold value, the rectifier element inside the resonance module 1 is triggered to be switched on or switched off according to the value of the direct current bus current and the charging and discharging state of the resonance module, so that each phase of the alternating current power supply is alternatively switched on independently with any one of the other two phases or is switched on simultaneously with the other two phases.

Fig. 4 is a structural diagram of a frequency conversion circuit for implementing harmonic suppression according to another embodiment of the present invention, in order to implement reduction of the cut-off angle of the rectifying element in the rectifying module, as shown in fig. 4, the resonant module 1 includes:

the first inductor Lu, the second inductor Lv and the third inductor Lw are connected in series, wherein the first inductor Lu is connected in series with a first phase U of an alternating current power supply, the second inductor Lv is connected in series with a second phase of the alternating current power supply, and the third inductor Lw is connected in series with a third phase of the alternating current power supply; the first capacitor C1, the second capacitor C2 and the third capacitor C3, the first capacitor C1 is connected between a first phase U of the alternating current power supply and a second phase of the alternating current power supply, the second capacitor C2 is connected between a second phase V of the alternating current power supply and a third phase W of the alternating current power supply, and the third capacitor C3 is connected between the first phase U of the alternating current power supply and the third phase W of the alternating current power supply.

The first inductor Lu, the second inductor Lv and the first capacitor C1 form a charge-discharge loop, and the charge-discharge loop is used for charging and discharging the first capacitor C1; the second inductor Lv, the third inductor Lw and the second capacitor C2 form a charge-discharge loop, and the charge-discharge loop is used for charging and discharging the second capacitor C2; the first inductor Lu, the third inductor Lw and the third capacitor C3 form a charge-discharge loop for charging and discharging the third capacitor C3.

In the present embodiment, the first capacitor C1, the second capacitor C2, and the third capacitor C3 are all ac thin film capacitors.

In order to save the device cost, the rectifier module is an uncontrolled rectifier module and comprises a first rectifier bridge, a second rectifier bridge and a third rectifier bridge which are arranged in parallel; the upper bridge arm of each rectifier bridge and the lower bridge arms of the other two rectifier bridges form different conduction loops respectively, and the conduction loops are used for controlling conduction between any two phases of the alternating current power supply.

Specifically, as shown in fig. 4, an upper bridge arm of the first rectifier bridge is formed by a first rectifier element VD1, a lower bridge arm of the first rectifier bridge is formed by a fourth rectifier element VD4, and a first phase U of the ac power supply is connected between the upper bridge arm and the lower bridge arm of the first rectifier bridge; an upper bridge arm of the second rectifier bridge is composed of a third rectifier element VD3, a lower bridge arm of the second rectifier bridge is composed of a sixth rectifier element VD6, and a second phase V of the alternating-current power supply is connected between the upper bridge arm and the lower bridge arm of the second rectifier bridge; and an upper arm of the third rectifier bridge is composed of a fifth rectifier element VD5, a lower arm of the third rectifier bridge is composed of a second rectifier element VD2, and a third phase W of the alternating-current power supply is connected between the upper arm and the lower arm of the third rectifier bridge. The rectifying element may be a diode.

When the value of the direct current bus current is less than or equal to the preset threshold value, it indicates that the load operates under low load, the rectifier module triggers the internal rectifier element to be switched on or switched off according to the value of the direct current bus current and the charging and discharging state of the resonance module 1, so as to realize that any two phases in the alternating current power supply are switched on at intervals of preset duration and switched off after the preset duration, and the method comprises the following steps: at the initial moment, current passes between the third phase W and the first phase U of the alternating current power supply, so that the voltage at two ends of the third capacitor C3 is equal to the load voltage, and the fifth rectifying element VD5 and the fourth rectifying element VD4 are triggered to be conducted; after a preset time, the direct current bus current is changed to zero, the fifth rectifying element VD5 and the fourth rectifying element VD4 are triggered to be cut off, meanwhile, the first inductor Lu and the second inductor Lv charge the first capacitor C1 in the forward direction, and the second inductor Lv and the third inductor Lw charge the second capacitor C2 in the reverse direction;

after a preset time interval, the voltage across the second capacitor C2 is reduced to a negative load voltage, and the fifth rectifying element VD5 and the sixth rectifying element VD6 are triggered to be conducted; after the preset duration, the direct current bus current is changed to zero, the fifth rectifying element VD5 and the sixth rectifying element VD6 are triggered to be cut off, the first capacitor C1 keeps charging in the positive direction, and the third capacitor C3 starts to discharge to the first inductor Lu and the third inductor Lw;

after a preset time interval, the voltage at two ends of the first capacitor C1 rises to the load voltage, the first rectifying element VD1 and the sixth rectifying element VD6 are triggered to be switched on, after the preset time interval is continued, the direct current bus current is changed to zero, the first rectifying element VD1 and the sixth rectifying element VD6 are triggered to be switched off, meanwhile, the second inductor Lv and the third inductor Lw start to charge the second capacitor C2 in the positive direction, and the third capacitor C3 discharges;

after a preset time interval, the voltage of the two ends of the third capacitor C3 is dropped to a negative load voltage, the first rectifying element VD1 and the second rectifying element VD2 are triggered to be switched on, after the preset time interval is continued, the direct current bus current is changed to zero, the first rectifying element VD1 and the second rectifying element VD2 are triggered to be switched off, meanwhile, the first capacitor C1 starts to discharge to the first inductor Lu and the second inductor Lv, and the second capacitor C2 continues to be charged in the positive direction;

after a preset time interval, the voltage at two ends of the second capacitor C2 rises to the load voltage, the third rectifying element VD3 and the second rectifying element VD2 are triggered to be switched on, after the preset time interval is continued, the direct current bus current is changed to zero, the third rectifying element VD3 and the second rectifying element VD2 are triggered to be switched off, meanwhile, the first capacitor C1 continues to discharge, and the first inductor Lu and the third inductor Lw start to charge the third capacitor C3;

after a preset time interval, the voltage of two ends of the first capacitor C1 is dropped to a negative load voltage, the third rectifying element VD3 and the fourth rectifying element VD4 are triggered to be switched on, after the preset time interval is continued, the direct current bus current is changed to zero, the third rectifying element VD3 and the fourth rectifying element VD4 are triggered to be switched off, meanwhile, the second capacitor C2 starts to discharge to the second inductor Lv and the third inductor Lw, and the third capacitor C3 continues to be charged;

after a preset time interval, the voltage at the two ends of the third capacitor C3 rises to the load voltage, the fifth rectifying element VD5 and the fourth rectifying element VD4 are triggered to be conducted, and the next cycle of the alternating current power supply is started; the initial time is the time when the phase angles of the three phases of the alternating-current power supply are all zero, and the preset time length is 1/12 of the period. The load in this embodiment may specifically be a motor of the compressor.

In specific implementation, a person skilled in the art can design the inductance values of the first inductor Lu, the second inductor Lv, and the third inductor Lw and the capacitance values of the first capacitor C1, the second capacitor C2, and the third capacitor C3 according to the actual three-phase current and the expected charging time, so as to realize the charging and discharging state at the above time.

As shown in fig. 4 mentioned above, the first inductor Lu, the second inductor Lv, and the third inductor Lw are respectively connected in series to the input terminals of the first phase U, the second phase V, and the third phase W of the ac power source, the first phase U outputs a current iu, the second phase V outputs a current iv, and the third phase W outputs a current iw, and the first capacitor C1, the second capacitor C2, and the third capacitor C3 may be ac thin-film capacitors respectively connected in parallel between the first phase U and the second phase V, between the second phase V and the third phase W, and between the first phase U and the third phase W of the ac power source. The resonance module 1 is formed by the devices, power factor correction (namely passive PFC) is realized, an uncontrolled rectifier element is adopted to replace a high-frequency PWM rectifier module, the cost of the controller is reduced, and the software control difficulty is reduced. In the process, the parallel capacitor can effectively raise the direct current bus voltage, and the influence of too low bus voltage on software control caused by counter electromotive force of the compressor is reduced.

The operation triggered at different times in the case of a small load is shown in table 1 below:

TABLE 1 operation triggered at different times under light load

Fig. 5 is a waveform diagram of an input current of an ac power supply according to an embodiment of the present invention, and the following describes operations triggered at different times with reference to fig. 5 and table 1 above:

at the time t0, current passes between the third phase W and the first phase U of the alternating current power supply, so that the voltage across the third capacitor C3 is equal to the load voltage, and the fifth rectifying element VD5 and the fourth rectifying element VD4 are triggered to be conducted; at the time t1, when the direct current bus current i0 ═ iw + iv/2 changes to zero, the fifth rectifying element VD5 and the fourth rectifying element VD4 are triggered to be turned off, meanwhile, the first capacitor C1 starts to be charged in the forward direction, and the second inductor Lv and the third inductor Lw charge the second capacitor C2 in the reverse direction;

at the time t2, the voltage across the second capacitor C2 drops to a negative load voltage, triggering the fifth rectifying element VD5 and the sixth rectifying element VD6 to conduct; at the time t3, when the direct current bus current iw + iu/2 changes to zero, the fifth rectifying element VD5 and the sixth rectifying element VD6 are triggered to be cut off, the first capacitor C1 keeps charging in the positive direction, and the third capacitor C3 starts to discharge to the first inductor Lu and the third inductor Lw;

at the time t4, the voltage across the first capacitor C1 rises to the load voltage, triggering the first rectifying element VD1 and the sixth rectifying element VD6 to be turned on, and at the time t5, when the direct current bus current i0 ═ iu + iw/2 changes to zero, triggering the first rectifying element VD1 and the sixth rectifying element VD6 to be turned off, and at the same time, the second inductor Lv and the third inductor Lw start to charge the second capacitor C2 in the forward direction, and the third capacitor C3 discharges;

at the time t6, the voltage across the third capacitor C3 drops to a negative load voltage, triggering the first rectifying element VD1 and the second rectifying element VD2 to be turned on, and at the time t7, when the direct current bus current i0 ═ iu + iv/2 changes to zero, triggering the first rectifying element VD1 and the second rectifying element VD2 to be turned off, and at the same time, the first capacitor C1 starts to discharge to the first inductor Lu and the second inductor Lv, and the second capacitor C2 continues to be charged in the forward direction;

at the time t8, the voltage across the second capacitor C2 rises to the load voltage, triggering the third rectifying element VD3 and the second rectifying element VD2 to be turned on, and at the time t9, when the direct current bus current i0 ═ iv + iu/2 changes to zero, triggering the third rectifying element VD3 and the second rectifying element VD2 to be turned off, and at the same time, the first capacitor C1 continues to discharge, and the first inductor Lu and the third inductor start to charge the third capacitor C3;

at the time t10, the voltage across the first capacitor C1 drops to a negative load voltage, triggering the third rectifying element VD3 and the fourth rectifying element VD4 to be turned on, at the time t11, the direct current bus current i0 ═ iv + iw/2 changes to zero, triggering the third rectifying element VD3 and the fourth rectifying element VD4 to be turned off, and at the same time, the second capacitor C2 starts to discharge to the second inductor Lv and the third inductor, and the third capacitor C3 continues to be charged;

at the time t12, when the voltage at the two ends of the third capacitor C3 rises to the load voltage, the fifth rectifying element VD5 and the fourth rectifying element VD4 are triggered to be conducted, and the next period of the alternating current power supply is started; t0 represents the time when the phase angles of the three phases of the ac power supply are all zero, and the interval between any two times is 1/12 cycles. Fig. 6 is a comparison diagram of an actual waveform of an input of the frequency conversion circuit for realizing harmonic suppression according to the embodiment of the present invention and a sine wave, and as shown in fig. 6, after the frequency conversion circuit for realizing harmonic suppression according to the embodiment of the present invention is adopted, the actual waveform of the input of the frequency conversion circuit reduces a cut-off angle of a rectifying element, is closer to the sine wave, and effectively suppresses harmonics.

Table 2 below is the operation triggered at different times under heavy load conditions:

TABLE 2 operation triggered at different times under heavy load

In the following, with reference to table 2, how to trigger the switching on or off of the internal rectifying element according to the charging/discharging state of the resonant module 1 under a heavy load condition so as to alternately switch on each phase of the ac power supply independently from any one of the other two phases or simultaneously switch on the other two phases is described:

at the time t0, the voltage across the second capacitor C2 is a negative load voltage, and the fifth rectifying element VD5 and the sixth rectifying element VD6 are triggered to be turned on; the third phase W and the second phase V of the alternating current power supply are independently conducted, the first inductor Lu and the second inductor Lv charge the first capacitor C1 in a forward direction, and at the time of t1, the voltage across the first capacitor C1 rises to the load voltage, and the first rectifying element VD1 is triggered to be conducted, so that the first phase U, the third phase W and the second phase V of the alternating current power supply are simultaneously conducted, and the second capacitor C2 starts to charge in the forward direction;

at the time t2, when the voltage across the second capacitor C2 rises to be greater than the negative load voltage, the fifth rectifying element VD5 is triggered to turn off, so that the first phase U and the second phase V of the ac power supply are independently conducted, and the third capacitor C3 starts to charge; at the time t3, the third capacitor C3 is charged to the load voltage, and the second rectifying element VD2 is triggered to conduct, so that the first phase U, the second phase V and the third phase W of the ac power supply are conducted simultaneously, and the first capacitor C1 starts to discharge to the first inductor Lu and the second inductor Lv;

at the time t4, when the voltage of the first capacitor C1 is reduced to be smaller than the load voltage, the sixth rectifying element VD6 is triggered to be cut off, so that the first phase U and the third phase W of the alternating current power supply are independently conducted, and meanwhile, the second capacitor C2 continues to be charged in the forward direction; at the time t5, the voltage at the two ends of the second capacitor C2 rises to the load voltage, and the third rectifying element VD3 is triggered to conduct, so that the second phase V of the ac power supply is conducted with the first phase U and the third phase W at the same time, and the third capacitor C3 starts to discharge to the first inductor Lu and the third inductor at the same time;

at the time t6, the voltage at two ends of the third capacitor C3 is lower than the load voltage, the first rectifying element VD1 is triggered to cut off, so that the second phase V and the third phase W of the alternating current power supply are independently conducted, the first capacitor C1 is charged reversely, at the time t7, the voltage at two ends of the first capacitor C1 is dropped to the negative load voltage, the fourth rectifying element VD4 is triggered to be conducted, so that the second phase V of the alternating current power supply is conducted with the first phase U and the third phase W at the same time, and meanwhile, the second capacitor C2 starts to discharge to the second inductor Lv and the third inductor;

at the time t8, when the voltage at the two ends of the second capacitor C2 is reduced to be smaller than the load voltage, the second rectifying element VD2 is triggered to be cut off, so that the second phase V and the first phase U of the alternating current power supply are independently conducted, and meanwhile, the third capacitor C3 is reversely charged; at the time t9, the voltage across the third capacitor C3 drops to a negative load voltage, triggering the fifth rectifying element VD5 to conduct, so that the third phase W of the ac power supply is conducted simultaneously with the first phase U and the second phase V, and the first capacitor C1 is charged in the forward direction;

at the time t10, when the voltage across the first capacitor C1 rises to be greater than the negative load voltage, the third rectifying element VD3 is triggered to be turned off, so that the third phase W and the first phase U of the ac power supply are independently turned on, and the second inductor Lv and the third inductor reversely charge the second capacitor C2; at the time t11, the voltage at the two ends of the second capacitor C2 drops to a negative load voltage, and the sixth rectifying element VD6 is triggered to conduct, so that the third phase W, the second phase V and the first phase U of the ac power supply are conducted at the same time, and the first inductor Lu and the third inductor start to charge the third capacitor C3 in the forward direction;

at time t12, the voltage across the third capacitor C3 rises to a voltage greater than the negative load voltage, triggering the fourth rectifying device VD4 to turn off, so that the third phase W and the second phase V of the ac power supply are independently conducted, and the next cycle of the ac power supply is started.

Example 3

The present embodiment provides a frequency converter, which includes the frequency conversion circuit for realizing harmonic suppression in the above embodiments. The method is used for reducing the cut-off angle of the rectifying element in the rectifying module, so that the input waveforms of the frequency conversion circuit are closer, and the harmonic waves are effectively suppressed.

Example 4

The embodiment provides a compressor, which comprises a load and a frequency converter, wherein the load is a motor, and the frequency converter is used for suppressing harmonic waves and improving the quality of electric energy input into the compressor.

Example 5

The embodiment provides an air conditioning equipment, which comprises the compressor in the above embodiments, and is used for improving the quality of electric energy input by the whole air conditioning equipment so as to improve the reliability of the equipment.

The above-described circuit embodiments are only illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.